Such hydrostatic open circuit driving gears with so-called primary adjustment and so-called secondary adjustment are known. If the primary unit (pump) is controlled to produce a constant working pressure it is important for the control of the speed of the secondary part (motor) that the latter, as a result of the constant working pressure delivered by the primary unit, always delivers at its output shaft a torque for the actuator proportional to its swept volume setting as long as the loss factors are negligible (book by Jean Thoma, "Hydrostatische Getriebe", Karl-Hanser-Verlag, Munich 1964, p. 68 to 70). If the direction of the flow of energy is to change in this kind of driving gear having an open circuit, i.e. if the motor (secondary unit) is to operate as the pump and the pump (primary unit) as the motor, the direction of rotation of the pump and motor has to be changed and both the primary and the secondary unit must be tilted through the zero-displacement centre position to change their displacement setting. A change in the direction of the flow of energy, in particular in braking operation, while maintaining the input and output direction of rotation is not possible in a hydrostatic driving gear of this kind without specific control organs (olhydraulik und Pneumatik, Publication Series, Volume 1, Grundschaltplane hydraulische Anlagen (Basic circuits, hydraulic plants), 1963, pp. 74, 75). With the change in direction of the flow of energy by reversing the direction of flow in the working pressure line, made possible by tilting the pump through the zero-position to negative displacement (swept volume), there is still no teaching of how to obtain a braking operation, i.e. how an actuator can be retarded by such a driving gear without destroying the braking energy by exhausting and heating the returned working medium.